The present invention relates to a novel method for treating hair to endow it with novel appropriate properties.
As is well known in the art, the cosmetic qualities of hair can be improved by applying a variety of compositions based on one or more active compounds to endow it with a variety of properties such as, for example, shine, easy disentangling, volume, hold, suppleness, vitality or softness.
To be properly effective, the active compounds of such compositions should, of course, have a certain affinity for the keratinous fibres of the hair, and should also have good persistence.
In other words, such active compounds should as far as possible remain fixed to the hair in a quantity sufficient to endow it with the desired properties.
However, since such active principles are not irreversibly fixed but are only fixed by adsorption, they are gradually eliminated by desorption during successive washes using shampoo.
To improve the persistence, studies have primarily been based on treatments which tend to cause a large proportion of the active principles to penetrate into the fibres, either by selecting such active principles which have a particular affinity for the fibres, or by modifying the fibres to increase their porosity and encourage penetration.
Thus coloration of hair keratin fibres is known to be improved by carrying out coloration simultaneously with permanent-waving. Reduction of the disulphide bonds of the keratin at depth permits the colorant to penetrate deeper and thus produces a certain durability of coloration.
This type of treatment, however, is not without serious disadvantages as it causes substantial degradation not only of the surface condition of the keratinous fibres, but also of their intrinsic mechanical properties.
As a result of a great deal of research in this field with a regard to remedying the disadvantages encountered until now, it has surprisingly and unexpectedly been shown that excellent results could be obtained when fixing active compounds to keratinous hair fibres without them suffering detrimental degradation. This has been achieved by limiting reactive site formation to only the surface of the keratinous hair fibres using a reducing agent employed under conditions and in proportions such that reactive sites are only generated at the periphery of the surface of the keratinous fibres.
It has actually been shown that the creation of reactive sites only on the surface is sufficient, and that they are remarkably reactive, to result in good fixing of a variety of active compounds by means of covalent bonds, without the original mechanical properties of the hair being substantially modified.
Thus the subject of the present invention is a novel method for treating keratinous hair fibres with a view to endowing them with novel appropriate properties, the method comprising steps consisting in reducing the disulphide bonds of the keratin with a view to generating reactive sites only on the surface to a depth of less than 10 xcexcm and to covalently fix to said reactive sites at least one active compound capable of endowing the keratinous hair fibres with novel appropriate properties, said active compound comprising at least one reactive function capable of reacting with said sites formed at the surface of the keratinous fibres.
In accordance with the invention, the treatment method can be carried out either in two separate steps, namely reducing the disulphide bonds of the keratin in a first step, and fixing the active compound by covalent bonds in a second step, or in a single step consisting in simultaneously reducing the disulphide bonds of the keratin and fixing the active compound.
In a further aspect, the treatment method of the invention envisages first applying the active compound to the keratinous hair fibres and then reducing the disulphide bonds of the keratin.
The essential characteristic of the method of the invention is to form reactive sites only on the surface of the keratinous hair fibres using a reducing composition.
A variety of conventional reducing agents can be used to this end, but their nature and concentration and method of application must be such that reactive sites are only generated on the surface of the keratinous substrate.
In other words, the reducing composition must not react beyond a depth of 10 xcexcm, preferably not beyond an average depth of 4 to 5 xcexcm, approximately corresponding to its cuticle.
These are, of course, average values which can vary depending on the type of treatment and which can thus be substantially lower or substantially higher than those indicated.
The reactive sites generated at the surface of the keratinous fibres are nucleophilic in nature and are essentially thiol functions.
In accordance with the invention, the reduction can be such that it generates between 0.1% and 5% by weight of cysteine with respect to the total amino acids of the keratinous fibres, preferably between 0.1% and 2% by weight.
Non limiting examples of hair keratin reducing agents which can be cited are:
thiols such as thioglycolic acid, thiolactic acid, 3-mercaptopropionic acid, thiomalic acid, 2,3-dimercaptosuccinic acid, cysteine, N-glycyl-L-cysteine, L-cysteinylglycine and their esters and salts, thioglycerol, cysteamine and its C1-C4 acylated derivatives, N-mesylcysteamine, N-acetylcysteine, N-mercaptoalkylamides of sugars such as N-(2-mercaptoethyl)gluconamide, pantetheine, the N-(mercaptoalkyl)-xcfx89-hydroxyalkylamides described in patent application EPt-A-0 354 835, the N-mono or N,N-dialkyl-4-mercapto butyramides described in patent application EP-A-0 368 763, the aminomercaptoalkylamides described in patent application EP-A-0 432 000, the derivatives of N-mercaptoalkyl)succinamic acid and N-(mercapto-alkyl)succinimides described in patent application EP-A-0 465 342, the alkylamino mercaptoalkylamides described in patent application EP-A-0 514 282, the azeotropic mixture of 2-hydroxypropyl thioglycolate and (2-hydroxy-1-methyl)ethyl thioglycolate described in patent application FR-A-2 679 448, the mercaptoalkylaminoamides described in patent application FR-A-2 692 481, and the N-mercaptoalkyl-alkanediamides described in patent application EP-A-0 653 202;
hydrides such as sodium or potassium borohydride;
alkali or alkaline-earth metal sulphites or bisulphites;
phosphorus derivatives such as phosphines or phosphites;
hyperbranched polymers and dendrimers carrying terminal thiol functions, such as those described in patent application FR 97 04085 and having formula (I): 
where:
Y represents an oxygen atom or an NH group;
A represents a linear, branched or cyclic, saturated or unsaturated C1-C12 alkane di-yl group;
this alkane di-yl group can optionally be interrupted by one or more heteroatoms, such as 0 or N;
this alkane di-yl group can optionally be substituted by:
an amino function: xe2x80x94NH2, optionally in the form of a salt of a mineral or organic acid;
an acylamino function: xe2x80x94NHxe2x80x94COR, where R represents a linear, branched or cyclic, saturated or unsaturated C1-C10 alkyl group;
a carboxylic acid function;
a C1-C10 ester function;
X represents a nucleophilic group.
In a particular preferred embodiment of the method of the invention, the reducing agent is a phosphine or a salt of a phosphine and a mineral or organic acid.
Among the phosphines which have provided particularly advantageous results as regards the formation of reactive sites on the surface of keratinous hair fibres, mention may be made of those with formula: 
where:
R1, R2 and R3, which are identical represent:
(a) xe2x80x94(CH2)nxe2x80x94CH3 
(c) xe2x80x94(CH2)nxe2x80x94COOR
(d) xe2x80x94(CH2)nxe2x80x94CONRRxe2x80x2 and
(e) xe2x80x94(CH2)nxe2x80x94NRRxe2x80x2
n=1 to 3
m=0 or 1 to 3
R and Rxe2x80x2, which may be identical or different, represent a hydrogen atom or a linear or branched C1-C4 alkyl radical, and salts of said compounds with formula (II).
Salts of phosphines with formula (II) which can be cited include hydrochlorides, hydrobromides, sulphates, citrates, oxalates and acetates.
Phosphines with general formula (II) which are particularly preferred and which can be cited include tris(2-carboxyethyl)phosphine and tris(hydroxymethyl)-phosphine which have the particular advantage not only of being odourless and water-soluble but also of being stable towards oxygen.
Phosphines with general formula (II) are known and have been described in particular in patents U.S. Pat. No. 3,754,035 and U.S. Pat. No. 3,489,811, as well as in EP-A-0 339 217 and in the publication by J. A. Burns et al., J.O.C. 56, 2648-2650 (1991).
The reducing agent is preferably used in aqueous solution under conditions such that its penetration is low to limit the reduction of disulphide bonds to the surface only.
When using a thiol such as thioglycolic acid, for example, its concentration is generally in the range 0.05 to 0.5 M, the pH of the aqueous solution is preferably in the range 6.5 to 9, and the contact time is generally in the range 1 to 10 minutes and preferably in the range 2 to 5 minutes, the pH being adjusted using an agent selected, for example, from: aqueous ammonia, monoethanolamine, diethanolamine, triethanolamine, 1,3-propanediamine, an alkaline or ammonium carbonate or bicarbonate, an organic carbonate such as guanidine carbonate, or an alkaline hydroxide, or advantageously using a polyquaternary ammonium hydroxide such as:
(a) homopolymers comprising units with the following formula (III) as the principal constituent of the chain: 
xe2x80x83where:
k and t are equal to 0 or 1, the sum k+t being equal to 1;
R4 and R5 each independently represent an alkyl radical containing 1 to 22 carbon atoms, a hydroxyalkyl radical where the alkyl group preferably contains 1 to 5 carbon atoms, or an amidoalkyl radical where the alkyl group preferably contains 1 to 5 carbon atoms;
or R4 and R5, together with the nitrogen atom to which they are attached, can represent heterocyclic radicals such as piperdyl or morpholinyl radicals;
R6 represents a hydrogen atom or a methyl radical;
(b) quaternary diammonium polymers containing repeat units with formula (IV): 
xe2x80x83where:
R7, R8, R9 and R10, which may be identical or different, represent aliphatic, alicyclic or arylaliphatic radicals containing 1 to 20 carbon atoms or C1-C5 lower hydroxyaliphatic radicals, or R7, R8, R9 and R10, taken together or separately, form heterocycles with the nitrogen atoms to which they are attached, optionally containing a second heteroatom other than nitrogen, or R7, R8, R9 and R10, represent a linear or branched C1-C6 alkyl radical substituted by a nitrile, ester, acyl, amide or xe2x80x94COOR11xe2x80x94Q or xe2x80x94COxe2x80x94NHxe2x80x94R11xe2x80x94Q function where R11 is an alkylene and Q is a quaternary ammonium group;
A and B represent linear or branched, saturated or unsaturated polymethylene groups containing 2 to 20 carbon atoms which may contain, bonded to or interposed in the main chain, one or more aromatic ring(s), one or more oxygen or sulphur atom(s), or sulphoxide, hydroxyl, quaternary ammonium, ureido, amide or ester groups;
A, R7 and R8 can further form a piperazine ring with the two nitrogen atoms to which they are attached; further, if A represents a linear or branched, saturated or unsaturated alkylene or hydroxyalkylene radical, B can also denote a xe2x80x94(CH2 )nxe2x80x94COxe2x80x94Dxe2x80x94OCxe2x80x94(CH2)n xe2x80x94group where D represents:
(i) a glycol residue with formula xe2x80x94Oxe2x80x94Zxe2x80x94Oxe2x80x94 where Z represents a linear or branched hydrocarbon radical, or a xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)xxe2x80x94CH2xe2x80x94CH2xe2x80x94 or xe2x80x94[CH2xe2x80x94CHxe2x80x94(CH3)xe2x80x94O]yxe2x80x94CH2xe2x80x94CHxe2x80x94(CH3)xe2x80x94 where x and y represent an integer from 1 to 4 corresponding to a defined and unique degree of polymerization, or any number from 1 to 4 corresponding to a mean degree of polymerization;
(ii) a bis-secondary diamine residue such as a piperazine derivative;
(iii) a bis-primary diamine residue with formula xe2x80x94NHxe2x80x94Yxe2x80x94NHxe2x80x94 where Y represents a linear or branched hydrocarbon radical or the divalent radical xe2x80x94CH2xe2x80x94CH2xe2x80x94Sxe2x80x94Sxe2x80x94CH2xe2x80x94CH2xe2x80x94;
(iv) a ureylene group with formula xe2x80x94NHxe2x80x94COxe2x80x94NHxe2x80x94;
(v) polyquaternary ammonium polymers constituted by units with formula (V): 
xe2x80x83where:
R11, R12, R13 and R14, which may be identical or different, represent a hydrogen atom, a methyl, ethyl, propyl, xcex2-hydroxyethyl, xcex2-hydroxypropyl or xe2x80x94CH2xe2x80x94CH2xe2x80x94 (Oxe2x80x94CH2xe2x80x94CH2)qxe2x80x94OH radical, q being an integer from 0 to 6 and R11, R12, R13 and R14 not simultaneously being a hydrogen atom;
B1 represents a linear or branched, saturated or unsaturated polymethylene group containing 2 to 20 carbon atoms and containing, bonded to or interposed in the main chain, one or more aromatic ring(s) or one or more oxygen or sulphur atom(s), or sulphoxide, sulphone, disulphide, amino, alkylamino, hydroxyl, quaternary ammonium, ureido, amide or ester groups; B1 preferably represents a radical with formula
xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94,
xe2x80x83p represents an integer from about 1 to 6; E can be zero or represent a xe2x80x94(CH2)rxe2x80x94COxe2x80x94 group where r represents a number equal to 4 or 7.
of these polymers with formulae (III), (IV) and (V), those which are preferably used are selected from:
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical; A represents the radical xe2x80x94(CH2)3xe2x80x94 and B represents the radical xe2x80x94(CH2)6xe2x80x94;
the compound with formula (IV) where R7 and R8 represent the ethyl radical, R9 and R10 represent the methyl radical and A and B represent xe2x80x94(CH2)3xe2x80x94
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical and A and B represent xe2x80x94(CH2)3xe2x80x94;
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical and A and B represent xe2x80x94(CH2)6xe2x80x94;
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical; A represents the radical xe2x80x94(CH2)3xe2x80x94 and B represents the radical xe2x80x94(CH2)9xe2x80x94;
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical; A represents the radical xe2x80x94(CH2)3xe2x80x94 and B represents the radical xe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94;
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical; A represents the radical xe2x80x94(CH2)3 and B represents the radical xe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94;
the compound with formula (IV) where R7, R8, R9 and R10 represent the methyl radical; A represents the radical xe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94and B represents the radical xe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94Oxe2x80x94(CH2)2xe2x80x94;
the compound with formula (V) where R11, R12, R13 and R14 represent the methyl radical; B1 represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94 and E represents the radical xe2x80x94(CH2)4xe2x80x94COxe2x80x94;
the compound with formula (V) where R11, R12, R13 and R14 represent the methyl radical; B1 represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94 and E represents the radical xe2x80x94(CH2)7xe2x80x94COxe2x80x94;
the compound with formula (V) where R11, R12, R13 and R14 represent the methyl radical; B1 represents the radical xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94 and E has the value zero;
the compound with formula (III) where t=1 and k=0; R4 and R5 represent the methyl radical and R6 represents a hydrogen atom.
The polyquaternary ammonium hydroxides with formulae (III), (IV) and (V) are prepared from the corresponding polyquaternary ammonium halides (the halide being Clxe2x88x92 or Brxe2x88x92) using methods which are known per se, namely:
either exchange with a basic resin such as IRA 400 resin, DOWEX 1xc3x9710 resin, etc., in an aqueous medium;
or by precipitation of the halides in the form of silver bromide or chloride using silver oxide Ag2O in an aqueous medium.
When a hydride such as, for example, potassium borohydride is used, its concentration is generally in the range 0.01 to 0.5 M, the contact time is in the range 1 to 30 minutes, preferably in the range 2 to 15 minutes, and the pH of the aqueous solution is preferably in the range 7.5 to 9.5, the acidifying agent allowing the pH to be adjusted advantageously being boric acid.
When using a phosphorus derivative such as a phosphine, its concentration is generally in the range 10xe2x88x923 M to 1 M, preferably in the range 10xe2x88x922 M to 0.5 M, the contact time is generally in the range 30 seconds to 1 hour, preferably in the range 1 to 30 minutes, and the pH of the aqueous solution is preferably in the range 3 to 9, more particularly in the range 4 to 7.
When using a hyperbranched polymer or a dendrimer carrying thiol functions, its concentration is generally such that the thiol titre of the solution is generally in the range 100 to 5000 meq/l, preferably in the range 500 to 2000 meq/l, the contact time is generally in the range 30 seconds to 1 hour, preferably in the range 1 to 30 minutes, and the pH of the aqueous solution is preferably in the range 5 to 11, more particularly in the range 7.5 to 10.5.
The disulphide bond reduction step is generally carried out at room temperature, but it can also be carried out at a temperature of less than 60xc2x0 C.
Clearly, these different parameters concerning the concentration, pH, temperature and contact time are interdependent and clearly, due consideration in this respect should be given. - Thus, for example, an increase in the concentration or a rise in temperature will result in a substantial reduction in the contact time.
When the treatment method of the invention is carried out in two steps, after reducing the disulphide bonds of the keratin in the keratinous fibres, they can be rinsed with water before fixing the active compound.
The active compounds which can be covalently fixed on the nucleophilic functions generated can be of a highly varied nature and their choice depends on the desired properties. These active compounds can be used as they are if they possess functions which are capable of forming covalent bonds with the nucleophilic functions of the keratinous hair fibres.
When the active compounds which are to be fixed do not possess such functions, these are then first introduced into the active compound using known methods. The term xe2x80x9creactive functionxe2x80x9d means a known reactive group which permits the formation of a covalent bond (by reaction with nucleophilic functions, in this instance sulphydryl functions xe2x80x94SH) and which thus comprise one or more nucleofuge(s) X or one or more activated carbon(s) or bond(s). The following groups are the usual nucleofuges:
Cl, Br, F, xe2x80x94OSO3M, xe2x80x94OSO2 alkyl, xe2x80x94OSO2 aryl, xe2x80x94OSO2N(alkyl)2, xe2x80x94OR1, SR2, xe2x80x94SOR2, xe2x80x94SO2R2, xe2x80x94S+R2R3, xe2x80x94SCN, xe2x80x94SCOOR2, xe2x80x94NR2R3, N+R2R3R4, 
xe2x80x83where M represents a hydrogen atom, an alkali or an alkaline-earth metal or an ammonium residue;
R1 represents a hydrogen atom, a C1-C4 alkyl radical, a substituted or unsubstituted phenyl radical, the radical PO3H2 and its salts, or the acetyl radical;
R2, R3 and R4, which may be identical or different, represent a hydrogen atom, a C1-C4 alkyl radical or a substituted or unsubstituted phenyl radical.
Among the most well known reactive groups, the following can be cited:
mono- and dihalotriazines;
dihaloquinoxalines, dihalopyrimidines;
vinylsulphones or their xcex2-halo- or xcex2-sulpha-toethylsulphone precursors;
acrylates and methacrylates;
acrylamides and methacrylamides;
maleimides and halomaleimides;
epoxides and aziridine derivatives;
oxazolinium, imadozolium or thiazolidinium groups;
carboxylic or sulphonic acid halides;
esters;
carbamates;
anhydrides;
isothiocyanates and isocyanates;
lactones;
azlactones with structure: 
xe2x80x83where:
Z represents the residue of an active compound;
R15 and R16, which may be identical or different, represent a hydrogen atom, a C1-C12 alkyl radical, a C3-C12 cycloalkyl radical, a C5-C12 aryl radical, a C6-C26 arenyl radical comprising 0 to 3 heteroatoms selected from S, N and O, or R15 and R16 together form a carbocycle containing 4 to 12 atoms, and n is an integer in the range 0 to 3, etc.
Among the active compounds which can be covalently fixed on the keratinous hair fibres after reduction of the surface disulphide bonds, those which can be cited are agents which can colour them, protect them from external attacking factors (light, pollution, water), strengthen them, modify their form, give them body, volume, lightness, suppleness, softness or vitality, facilitate combing or disentangling, reduce static electricity or increase their shine, i.e., in general any agent which can protect them and/or improve their appearance and/or feel.
In particular, the following active compounds can be cited by way of example to illustrate the invention:
(a) reactive colorants intended to modify hair colour, such as:
compounds from the REMAZOL(copyright) range sold by DYSTAR;
compounds from the PROCION(copyright) range sold by ZENECA;
compounds from the CIBACRONE(copyright) and LANASOL(copyright) ranges sold by CIBA-GEIGY;
compounds from the LEVAFIX(copyright) range sold by BAYER.
The following examples can be cited more particularly:
Reactive Blue 4 (C.I. 61205);
Reactive Black 5 (C.I. 20505);
Reactive Blue 19 (C.I. 61200);
Reactive Orange 16 (C.I. 17757);
Reactive Red 4 (C.I. 18105);
Reactive Yellow 2 (C.I. 18972);
Reactive Yellow 135; and
Reactive Red 2 (C.I. 18200).
(b) reactive sunscreens from the benzylidenecamphor series, para-aminobenzoic acid derivatives and esters thereof, cinnamic acid derivatives and esters thereof, salicyl derivatives, benzophenone derivatives, dibenzoylmethane derivatives, benzotriazole or benzimidazole derivatives, anthranilic acid and its esters, anthranilate or cyanoacrylate derivatives, such as those with the following formulae, for example: 
Rxe2x80x2=methyl or tert-octyl 
Rxe2x80x3=H, C1-C6 alkyl, and
Y=NH or O 
R1=H or OH, and
y R2=OH or OCH3 
R4=H or xe2x80x94NHCOCHxe2x95x90CH2 
R5=H or C1-C12 alkyl 
(c) reactive shine agents, in particular silicon-containing polymers such as polydimethylsiloxane derivatives having, for example, vinyl, acrylic or epoxy reactive groups, etc.. Examples which can be cited are the divinylpolydimethylsiloxanes sold by Hxc3x9cLS-PETRARCH under reference numbers PS 441, PS 443, PS 445, PS 448 and PS 449.5 or the vinylmethyl polydimethylsiloxane copolymer by the same company under reference number PS 424;
(d) hydrophobic reactive compounds with a C8-C30 fatty chain, such as octadecyl methacrylate or acrylate or with a C2 to C18 perfluorinated chain, such as the FORALKYLS(copyright) AC6 and AC8, MAC6 and MAC8 sold by ELF ATOCHEM, hexafluoropropene oxide, methyl perfluoro-3-buteneoate, etc..
The active compound is generally present in aqueous solution in a concentration in the range 10xe2x88x923 to 20%, preferably in the range 10xe2x88x922 to 5%, and its pH is generally in the range 2 to 10, preferably in the range 4 to 9.
The contact time necessary for formation of the covalent bonds is generally in the range 1 minute to 1 hour, preferably in the range 1 to 30 minutes at room temperature or at a temperature of less than 60xc2x0 C.
The composition containing the reducing agent and the composition containing the active compound can also comprise various other additives.
Additives which can be cited in particular include nonionic, anionic, cationic or amphoteric surfactants, volatile or non-volatile, linear or cyclic silicones, polyorganosiloxanes, cationic polymers such as those used in the compositions of patents FR-A-2 472 382 and FR-A-2 495 931 and of patent LU-83703, basic or acidic amino acids, peptides, protein hydrolysates, waxes, C3-C6 alkanediols, C1-C5 lower alcohols, fatty alcohols, fatty acids, alkylene or dialkylene glycol alkyl ethers, glycerol, hydrophilic or lipophilic gelling agents, thickeners, suspension agents, opacifying agents, sequestering agents, colorants, sunscreens, fillers, pigments, odour absorbers, hair loss preventatives, anti-dandruff agents, antioxidants, vitamins, solvents, fragrances and preservatives.
These different additives are generally present in a proportion in the range 0.01% to 20% by weight of the total composition weight.
Some examples of the hair treatment method of the invention will now be given in order to illustrate the invention.